The only Intel CPU's with 8 or more cores are the Xeon CPU's and those are intended for the servers. So unless you're running a server og applications that are optimized for Hyperthreading then you do not need it. Not to mention that the Xeon CPU's are hella expensive.
Anyway, I have a top of the line Haswell i7-4770K and even that has only 4 cores. Which is more than enough.